Denture liner of bibulous paper impregnated with vinyl resin



Patented June 12, 1951 UNITED STATES TENT OFFICE DENTURE-LINER 0F BIBULOUS PAPER IM- PREGNATED WITH VINYL RESIN Maurice B. Brand, Chicago, II].

'No Drawing. Application September 9, 1949, Serial No. 114,903

of the wearer, it will, if properly made, fit'quite I snugly. However, in the course of time, say from six months to a year, there is the likelihood of the shrinking of the gums and changes in the palate of the wearer, with the result that thereafter the dentures are likely to become loose and misfitting.

Attempts have been made to guard against this, or to overcome the difficulty when it once 7' develops. Some of these attempts involve the use of so-called liquid or powdered so-called liners, which are usually composed of some form of plastic material which is of the same nature as the material of which the dentures are made, for example some form of methyl methacrylate resins. Most of these materials are furnished in the form of a paste or solution that is applied, either by the wearer or a dentist. to the dentures that have become too large. These materials,by reason of the fact that they contain volatile solvents, have a distinctly undesirable efiect upon the mucous membrane of the wearer, and cause stinging and burning sensations that are very disagreeable, and, in some cases, may even be harmful. "They are also difficult to use, and require frequent renewal. Such products are also messy and in most cases require replacement after each meal, such as is the case with many of the gum powders and sticky materials now on the market.

This problem is rather fully discussed .in the Journal of the American Dental Association for March, 1946,'vol. 33, pages 304-318, in which an analysis :of various liners for dentures are adescribed, and the analyses thereof disclosed.

All of the liners mentioned in the said articles have a base of a methyl methacrylate resin, dissolved in various types of solvents, such as ethyl acetate, amyl acetate, diethyl carbonate, tria cetin, etc. In all cases thesolvent .used must be evaporated for a considerable extent before the denture coated with the liner composition can, with any degree of safety, be placed in the mouth of the wearer. But even then, toxic reactions have been noted, and it is at present the general opinion of the dental profession that such liners which depend upon the evaporation and eventual elimination ofv solvents are not satisfactory. Examples of such types of liners have also been described in the Rogover Patent No. 2,377,041, in which a combination of a methyl methacrylate resin and triacetin is used.

In 'contradistinction to the aforementioned prior attempts to solve the denture liner problem, the present invention attacks it from a different angle, in providing a substantially dry sheet-like. material made of a composition that is sufiiciently adhesive to cling to the denture but which will not adhere to the membranes of the gums and palate, and which, moreover, is perfectly innocuous and tasteless, and which will serve the full purpose of making up for gum and palate changes.

It is therefore one of the objects of the present invention to provide a'denture liner in sheet form, which has the above-enumerated desirable properties.

A further object of the invention concerns a process for the manufacture of such liners.

A still further object is to provide a liner material in sheet form that may be applied by the wearer Without the use of any kinds of sol- .vents and without the intervention or assistance of a trained dentist, thus making it possible for the wearers of dentures to adjust them themselves in the privacy of their homes.

The denture liner of the present invention comprises a webbing of cellulosic material which acts not only as a reinforcing agent 'or skeleton for the liner, but also provides means for manufacturing it in a facile manner. The primary material of which the improved liner of the present invention is made is a suitable blend of a vinyl chloride-vinyl acetate copolymer resin and vinyl acetate resins, plus a suitable catalyst. By thus depositing the resins within the interstices of the "supporting medium, 'a product is obtained which has no solubility in any or the body fluids, such as saliva, and which is much more resistant than would be a film or impregnating medium that has merely been dissolved in an appropriate solvent and then allowed to evaporate.

As a skeletal supporting type of filler I prefer to employ a pure cellul'osic material, such as a strong but bibulous paper. For this purpose the type of paper commonly known as Japanese Yoshino paper or, as it is sometimes also known, Dental paper, is most suitable. This paper is impregnated with a solution containing both vinyl chloride-acetate copolymer resins in a low state of polymerization and similar vinylacet'ate resins, there preferably being also present a catalyst, such as benzoyl peroxide, which is U believed to initate a copolymerization or similar reaction between these two resins. A suitable plasticizer that does not impart any distinct taste or odor to the composition should also be employed to keep the eventual denture liner material soft and pliant.

One preferred embodiment of the present invention is as follows:

100 parts by weight of a vinyl chloride-vinyl acetate copolymer resin of the type commercially designated as VYLF (having an intrinsic viscosity of about 0.24 and containing about 87 vinyl chloride and 13% vinyl acetate) 20 parts by weight of a vinyl. acetate resin of the type commercially designated as AYAA (intrinsic viscosity 0.39)

parts of another vinyl acetate resin of the type commercially designated as AYAC (intrinsic viscosity 0.11)

3 parts by weight of benzoyl peroxide, and

16 parts by weight of dibutyl phthalate are all dissolved in 175 parts by weight of ethyl acetate. The solution is gently stirred for some time, say about one hour, the solution gradually becoming uniform. It should be pointed out that the entire operation is at room temperature.

The solution thus obtained is placed in a convenient vessel and bibulous paper is passed over the surface of the liquid, so that it will absorb a suitable amount of the liquid, the paper thereby becoming not only coated, but, by reason of its bibulous nature, also impregnated with the solution. The paper thus treated is then placed in a suitable drier so that the ethyl acetate may as far as possible evaporate. However, due to the solvent retention characteristics of the mixed resins, sufficient of the ethyl acetate will remain in the apparently dry sheets resulting from the process to give the same a certain tackiness which causes them to adhere to the denture when applied thereto and rubbed into contact therewith, also being sufiiciently plastic to retain an impression made therein.

If deemed desirable, a small amount, say about 1%, of a suitable preservative such as a naphthyl salicylate, may be added to the solution prior to, during, or after the solution has been made.

The sheets resulting from the practice of the process just described are translucent and slightly tacky. The user can cut pieces therefrom corresponding in size and general shape to the denture to which the material is intended to be applied, and the cut pieces are then placed in contact with those surfaces of the denture that normally contact either the gums or the palate, or both, of the wearer, being rubbed into good contact with the dentures, to which the material will closely cling. As the thickness of the sheets is on the order of from one one-thousandth to one and one-half one-thousandths of an inch, one or more sheets may be applied to obtain the desired dimensional increase in the denture, which will thus fit more accurately into the wearers mouth.

An application of the denture liners of the present invention may last up to six months, whereafter the applied material may readily be removed from the denture, as by scraping with a knife, and a new layer applied. Or further layers may simply be applied over the material that has previously been placed on the denture.

As the composition with which the bibulous paper has been impregnated is perfectly tasteless, odorless, substantially free from irritating adapt and fit itself to the exact shape of the gums and palate of the wearer. It also prevents small crumbs and other food particles from working into the interface of the denture and the gums and palate. As the material is entirely non-toxic, and compatible with methyl methacrylate resin dentures, which are the type most usually used at this period of the dental arts, but is without solvent or softening action thereon, it forms a very desirable and effective liner for the intended use.

The proportions given above, while variable within reasonable limits, are critical, and there should be at least about five times as much of the vinyl chloride resin VYLF as of the vinyl acetate resin AYAA, while the resin of type AYAC should be about half the quantity of resin AYAA. It appears that the molecular weight of the resin mixture produced is just about right for the present purpose. If the molecular weight is too low, then the product is too soft, while if it were too high, the material tends to be too hard and brittle, and might develop cracks in use, which would be quite undesirable as these might harbor deleterious baceteria.

As the product of the present invention is perfectly insoluble in water, and not affected by saliva and other oral secretions, and resistant to tooth paste and other cleaners often used in dental hygiene, it is perfectly adapted for its intended use. Also, the dentures may be used immediately after the attachment of the material, and they can be washed even with hot water.

The method of coating or impregnating the bibulous paper is open to a wide choice, and any suitable available coating or impregnating instrumentality may be employed. As these are well known, it is not deemed necessary to illustrate the present invention with drawings.

It should be pointed out that the designations of the vinyl resins are not trade-marks, but are the commercial identifying grade marks employed by the manufacturers. Most of these resins are fully described as to their nature and characteristics in the third edition of The Condensed Chemical Dictionary, 1942, page 663, under the entry Vinylite, which latter name, however, is a trade-mark.

Further descriptions appear in the technical bulletins of the manufacturers and on pages 462- 464 of the 1946 Edition of Zimmerman & Lavines Handbook of Material Trade Names.

Of course, vinyl resins of other manufacture, may be used.

Accordingly applicant claims:

1. An impregnating solution for impregnating bibulous paper for the production of denture liners which comprises substantially the following amounts of materials:

parts by weight of a vinyl chloride-vinyl acetate copolymer resin containing about 87% of vinyl chloride and about 13% of vinyl acetate and having an intrinsic viscosity of about 0.24.

20 parts by weight of vinyl acetate resin having an intrinsic viscosity of about 0.39

10 parts by weight of vinyl acetate resin having an intrinsic viscosity of about 0.11

3 parts by weight of benzoyl peroxide,

16 parts by weight of dibutyl phthalate, and about parts by weight of ethyl acetate.

2. A denture liner consisting of thin bibulous paper impregnated with a mixture of (a) a vinyl chloride-vinyl acetate co-polymer resin containing about 87% of vinyl chloride and about 13% of vinyl acetate and having an intrinsic viscosity of about 0.24, (b) vinyl acetate resin having an intrinsic viscosity of about 0.39, (0) vinyl acetate resin having an intrinsic viscosity of about 0.11, there being about five times as much of said resin (a) as of said resin (1)), and about onehalf as much resin (0) as resin (1)); and a sufficient amount of a plasticizer to keep the said mixture soft and pliant.

3. A denture liner consisting of thin bibulous paper impregnated with a composition comprising the following materials in about the proportions recited, as follows: 100 parts by weight of a vinyl chloride-vinyl acetate co-polymer resin containing about 87% of vinyl chloride and about 13% of vinyl acetate and having an intrinsic viscosity of about 0.24; about 20 parts by weight of vinyl acetate resin having an intrinsic viscosity of about 0.39; about 10 parts by weight of vinyl acetate resin having an intrinsic viscosity of about 0.11; about 3 parts by weight of benzoyl peroxide; and about 16 parts by weight of dibutyl phthalate.

4. A denture liner as defined in claim 2 in which the bibulous paper is that known as Yoshino.

5. A denture liner as defined in claim 3 in which the bibulous paper is that known as Yoshino."

6. A denture liner consisting of a thin internal REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 2,045;963 Redman June 30, 1936 2,053,773 Freydberg Sept. 8, 1936 FOREIGN PATENTS Number Country Date 354,241 Germany June 6, 1922 460,887 Great Britain Jan. 28, 1937 558,470 Great Britain Jan. 6, 1944 OTHER REFERENCES Canadian Paint 8a Varnish Magazine, April 15, 1946, page 18. 

2. A DENTURE LINER CONSISTING OF THIN BIBULOUS PAPER IMPREGNATED WITH A MIXTURE OF (A) A VINYL CHLORIDE-VINYL ACETATE CO-POLYMER RESIN CONTAINING ABOUT 87% OF VINYL CHLORIDE AND ABOUT 13% OF VINYL ACETATE AND HAVING AN INTRINSIC VISCOSITY OF ABOUT 0.24, (B) VINYL ACETATE RESIN HAVING AN INTRINSIC VISCOSITY OF ABOUT 0.39, (C) VINYL ACETATE RESIN HAVING AN INTRINSIC VISCOSITY OF ABOUT 0.11, THERE BEING ABOUT FIVE TIMES AS MUCH OF SAID RESIN (A) AS OF SAID RESIN (B), AND ABOUT ONEHALF AS MUCH RESIN (C) AS RESIN (B), AND A SUFFICIENT AMOUNT OF A PLASTICIZER TO KEEP THE SAID MIXTURE SOFT AND PLIANT. 